1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD panel and a method for manufacturing the same in which light leakage is prevented from occurring in an array peripheral region, thereby improving picture quality.
2. Background of the Related Art
Recently, an LCD device, one of flat panel devices, has received much attention. The LCD device changes an optical anisotropy by applying an electric field to a liquid crystal having liquidity of a liquid and optical characteristic of a crystal. The LCD device can achieve miniaturization, high resolution, large sizing, and lower power consumption compared with related art cathode ray tubes (CRTs).
The LCD panel of the LCD device generally includes a first substrate, a second substrate attached to the first substrate to oppose the first substrate, and a liquid crystal layer between the first and second substrates. If the first and second substrates are not aligned precisely with respect to each other, dotted images are generated at undesired portions of the panel due to light leakage.
To prevent light leakage from occurring in the panel, a black matrix is formed in at portions where a major light leakage occurs. However, there are limitations to prevent completely any light leakage from occurring in the LCD panels which is discussed below in more detail.
A related art LCD panel and a method for manufacturing the same will be described in the accompanying drawings.
A related art LCD panel includes an array region, an array peripheral region, and a pad region. These regions are well known in the art. The array region is an active region to drive the liquid crystal. In the array peripheral region, lines such as gate lines or data lines for transmitting signals are linked to each other. These linked lines are then connected with an external driving circuit in the pad region of the LCD panel.
FIG. 1 is a sectional view of a related art LCD panel. FIG. 2 is a sectional view of the LCD panel taken along line I-I′ of FIG. 1 to describe certain problems of the related art LCD panel.
Referring to FIG. 1 and FIG. 2, the related art LCD panel will be described in detail.
The related art LCD panel includes first and second substrates 10 and 20, and a liquid crystal layer 16.
In the first substrate 10, a plurality of gate lines 11 are formed at certain constant intervals, and a gate insulating film 12 is formed on the entire surface of the first substrate including the gate lines 11. A plurality of data lines 13 are formed at certain constant intervals on the gate insulating film 12 to cross the gate lines 11 in a matrix form, thereby defining a pixel region. Then, a capacitor metal layer 13a is formed simultaneously with each of the data lines 13 in a predetermined portion of each gate line 11 to provide a capacitor with the gate line 11. For each pixel area of the pixel region, a thin film transistor (TFT) is formed at a crossing point of the corresponding gate line 11 and the corresponding data line 13. Then, a passivation film 14 is formed on the entire surface of the first substrate including the TFT. A pixel electrode 15 electrically connected with the TFT is formed on the passivation film 14 at each pixel area of the pixel region.
The second substrate includes a color filter layer 18, a black matrix 19, and a common electrode 17. The color filter layer 18 is formed on the second substrate 20 to display color. Then the black matrix 19 is formed between the color filter layers 18 to prevent light from leaking. In the common electrode 17, an electric field is formed to drive the liquid crystal using the pixel electrode 15.
At this time, the gate lines 11 and the data lines 13 are respectively extended to a gate pad region and a data pad region of the pad region, and are connected with the external driving circuit.
Such an LCD panel includes a back light at the rear of the panel. When light from the back light passes through the panel, light leakage occurs at undesired portions, so that the display panel is partially dotted.
To solve the light leakage problem in the display panel, the edge of the pixel electrode is overlapped with the gate lines, or the black matrix 19 is additionally formed at portions where a significant light leakage occurs. However, as shown in FIG. 1, if the first and second substrates are not aligned precisely to each other, light leakage occurs at portions where the black matrix is not formed.
Furthermore, if a pattern of the liquid crystal is shifted or a disclination occurs during the formation of the liquid crystal pattern, a distortion in the liquid crystal occurs. At this time, light from the back light passes through the portions of the panel where the black matrix is not formed, thereby generating a device and operation defect.
Moreover, light leakage often occurs in the array peripheral region that generally corresponds to the four corners of the panel due to refractive characteristics of the light.